The sisters' mother and father only discovered their daughters’ night-time departure the next morning at 8am when they went into their room and found their beds empty.

After checking they had not gone to college early, the family contacted the police to report the girls missing.

Officers were able to trace the girls onto a flight to Istanbul in Turkey.

Days later the twins contacted their family from Syria and counter-terrorism investigators were alerted.

“The family have been trying to encourage the girls to come home but they have suggested that they have no intention of doing so,” intelligence sources told The Sun.

“The case has been picked up by Counter Terrorism Unit who believe there is no purpose for them to be in Syria other than terror purposes.

“It is confirmed that they are in Syria and being dealt with by CTU, who are investigating how they got there and what they are doing out there.”

Questions have been raised over how the girls found the cash to pay for their lengthy journey while still in full-time education.

Counter-terrorism officers are investigating whether they were “recruited” and bankrolled by jihadists in Syria.

Just last month the girls, from Chorlton, Manchester, took part in a university information day at Connell Sixth Form College, which they both attend.

An image of one of the twins working at a laptop was posted on the college’s Twitter page but later removed.

After the girls disappeared, a source told The Sun: “The girls travelled to Syria after an older brother, who is believed to be an Isis fighter, travelled to the country. The girls were not on the radar. They’ve gone abroad as they wanted to be with their brother.”

Neighbours expressed shock at the twins’ departure.

“How do two young girls afford to fly out of the country without anyone stopping them?” One said.

“There are eight or nine kids in the house but I only normally see the boys going in and out. The girls are kept indoors. They don’t socialise with the rest of the estate.”

Another added: “My son goes to the same school as the younger kids, they seemed nice enough but they don’t really mix with everyone.

“What is the world coming to? You would never imagine it happening on our doorstep.”

Both girls, thought to be of Somali origin, have been described as “extremely religious”.

Some friends claimed the girls were not allowed to be seen talking to boys.

Their family, who moved to Britain about ten years ago, have no far made no public comment.

A spokesman for Greater Manchester Police confirmed they had received a report about the girls disappearing.

He said: “The girls flew from Manchester International Airport to Istanbul. Since their departure the girls have been in contact with their family.

“We are attempting to confirm their current location and secure the well-being of both girls.